Hewlett-Packard 97  
Written by Accutron on 2015-06-13  

In 1976, Hewlett-Packard simultaneously introduced the HP-67 and HP-97, second-generation updates to HP's first programmable handheld calculator, the HP-65. Like the HP-65, the HP-67 is a card-programmable handheld, but the HP-97 has a portable desktop form factor, which adds a thermal printer and other improvements. Despite its form factor, the HP-97 has a large rechargeable NiCd battery, and is light and compact, making it an effective two-handed portable device. HP's 'Topcat' series, which includes the HP-97 and the non-programmable HP-91 and HP-92, are based on HP's second generation 'Woodstock' manufacturing techniques, but retain the 15-digit display of HP's first generation calculators. Woodstock series handheld calculators are equipped with a 12-digit display, on which the mantissa must share digits with the exponent. HP would not produce another calculator with a display possessing more than 12 digits until the introduction of the HP-18C in 1986. The HP-67 and HP-97 represented a total convergence of calculator functionality, immediately supplanting all of HP's previous small key-per-function machines.

The HP-97 is a unique among HP's 'personal calculator' product line (which excludes the HP-9100 and the large 9800-series industrial calculators and computers manufactured by HP's Loveland Calculator Division.) It is the only programmable personal desktop calculator ever built by HP, and the only HP personal calculator with both a card reader and a printer in a single mechanical package. The HP-97 has the highest key count of any HP personal calculator not equipped with an alphabetical keyboard - 14 more keys than the HP-91 and HP-92. Topcat series machines are also the only HP desktop calculators to be equipped with a battery. The HP-67 and HP-97 also introduced several critical programming improvements over the HP-65, including indirect addressing, fully merged key codes and the ability to read and write data on magnetic cards. The addition of indirect addressing is of particular importance as it, combined with the conditional branching capability inherited from the HP-65, elevates the HP-67 and HP-97 to the status of being true Turing-complete computers.

Although it is often crudely referred to as a 'desktop HP-67 with a printer', the HP-97 has a number of notable differences which make it a more usable and resilient calculator. Unlike HP handheld calculators, which all have metal dome switch pads with hinged plastic key caps, the HP-97 has linear travel coil spring keys. While the distinctive HP tactile feedback is absent, the linear keys are optimized for rapid data entry, and are not susceptible to the types of failures endemic to metal dome switches. The HP-97 also has 56 keys (scanned in a 4x14 array) and a single shift key, as opposed to the HP-67's 35 keys and three shift keys. This configuration means that more functions are unshifted on the HP-97, resulting in a lower average number of keystrokes per operation. The HP-97 is also equipped with a Printer Interface / Keyboard (PIK) IC, which not only drives the integrated thermal printer, but also includes a keyboard buffer which stores up to seven key codes, and debounces the keyboard by delaying key codes approximately 4.5ms.

Another design advantage, of particular interest to calculator collectors, is that the HP-97 is built to be easily repaired. It requires neither the removal of stickers or adhesive rubber feet to gain access to the interior of the unit, nor the application of razor blades, power drills, hair dryers or ultrasonic cleaners to perform basic servicing procedures.

HP later introduced the HP-97S I/O Calculator, an otherwise standard HP-97 with a rerouted logic PCA, designed to more easily accommodate a permanently attached BCD interface pod. After the introduction of the HP-97S, the HP-97 was built with the new PCA layout as well, and simply omitted the interface pod. These later units can be easily identified by the presence of unpopulated solder pads for a 16-pin DIP.

HP-97 Owner's Handbook and Programming Guide (PDF)
HP-97 Service Manual (PDF)
HP-67 & HP-97 Brochure (PDF)
HP-67 & HP-97 Comprehensive Software Support (PDF)

Hewlett-Packard 97 programmable desktop calculator.

HP-97 calculator, rear view. Note the card reader aperture.

HP-97 calculator, internal construction.

HP-97 Owner's Handbook and 00097-13101 Standard Pac software library.

HP Computer & Calculator Products (1966-1976)

HP Personal Calculator Production Timeline (1972-2003)

This article is part of the [Electronic Calculators] exhibit.

©2000-2019 The Vintage Technology Association. All rights reserved.